Control Principle of Motor Units in Neuro-Muscular Systems

为了使FES对瘫痪运动功能的恢复更加合理，需要对非线性、时变的肌肉收缩动力学进行建模。我们建立了一个激活模型，重点是钙释放和重新封存到肌浆网，包括钙诱导的钙释放。该模型在钙浓度上有两个稳定的平衡点。从低平衡点到高平衡点的变化可以由输入脉冲的高频序列产生，并且可以解释增强作用。该模型还表现出一种类似捕捉的效果，作为一个长期的肌肉力量的增加后，施加单脉冲。我们还开发了一种方法，从噪声信号中检测神经动作电位（AP）。这种方法可以应用于肌电的分解，肌电是运动单位的动作电位的群体。多分辨率分析用于低信噪比条件下的AP检测。使用多变量分析来估计来自多单元活动记录的单单元活动。由单个单元产生的AP具有取决于诸如光纤尺寸和光纤与记录电极之间的距离等因素的特征波形。因此，AP根据其波形被分类到每个单元中。

To make the FES-restoration of paralyzed motor function more rational, it is required that the nonlinear and time-variant muscle contraction dynamics is modeled. We built an activation model with emphasis on the calcium liberation from and re-sequestration into the sarcoplasmic reticulum, including calcium-induced calcium release. The model had two stable equilibrium points in the calcium concentration. Changes from the low to the high equilibrium point could be produced by high frequency trains of input pulses and would account for the potentiation. The model also showed a catch-like effect, as a long-lasting increment of muscle force after the application of single pulse.We also developed a method for detecting nerve action potentials (APs) from noisy signals. This method can be applied to the decomposition of electro-myograms, which are the population of action potentials from motor units. Multiresolution analysis was used for detecting APs under low SNR condition. Multivariate analysis was used to estimate single-unit activity from multi-unit activity recordings. APs produced by an individual unit have a characteristic waveform depending on factors such as the size of the fiber and the distance between the fiber and the recording electrode. Therefore, APs were classified into each unit based on their waveforms.